PROCESSING

The current practice at Chelopech is to use conventional three-stage crushing followed by a two-stage grinding circuit to prepare feed for selective flotation to extract a gold-rich copper concentrate. At present, the production of auriferous pyrite concentrate is not considered economic due to limited market demand.

Crushing
Run-of-mine ore is reduced using a traditional three-stage crushing circuit of primary jaw crushers and secondary and tertiary cone crushers, to produce a mill feed particle size of minus 16mm.
The jaw crusher discharge is transported by a belt conveyor to the primary double decked screen, whose top deck oversize forms the feed to the secondary crusher. The oversize from both decks of the secondary crusher screen forms part of the feed to tertiary crushers.
The tertiary crushers operate in closed circuit with their dedicated single screens fitted with 16mm mesh decks. The oversize from these screens forms the second component of feed to the tertiary crushers, joining the secondary crusher screen oversize. The undersize (minus 16mm) material from both the secondary and tertiary screens reports to the mill fine ore bin by conveyor.

Grinding
The crushed ore is drawn from the 2000t fine ore bin to feed the primary ball mill. The milling circuit comprises a primary (3.6m dia x 5.0m long) and a secondary (2.7m dia x 3.6m long) ball mill. The primary mill operates in closed circuit with cyclones, with underflow returned to the mill and the overflow gravitating to the secondary mill discharge sump. The combined secondary mill discharge and primary mill cyclone overflow are pumped to feed the secondary cyclones, which have an overflow product of p80 of 75 microns, is fed to the flotation circuit.

Flotation Circuit
The flotation is directly selective using lime for pyrite depression and whilst recovering the copper minerals (mainly tennantite and enargite).

The mill cyclone overflow reports to three Denver-500 banks of rougher float cells arranged in series. The concentrate from the first bank reports to final concentrate whilst the combined concentrate from the second and third banks is pumped to the Denver-30 cleaner banks, where three stages of cleaning are performed. The third cleaner concentrate passes to the concentrate handling section. The first cleaner tailings are recycled to the copper float feed. The rougher tailings are pumped to the Devnver-500 scavenger cell banks. The scavenger concentrate is also recycled to the copper float feed. Scavenger tailings report to final tailings.

Concentrate Handling
There are three 18m diameter thickeners for dewatering the final copper concentrate. The thickener overflow is sent to the water storage and distribution system and the thickener underflow is dewatered using a ceramic disc filter, with the filter cake reporting to the final concentrate bins.
Since much of the copper is present as the arsenical minerals, tennantite and enargite, the copper concentrate contains about 4-6% arsenic. This renders it unsuitable for smelting in the nearby Pirdop smelter and, at present, it is shipped overseas. The filter cake has a moisture content of 7-9.5% on average, which is designed to meet the shipping/customer requirements.
The concentrate produced at the site is loaded on covered trucks and transported by road to the town of Zlatitza, where it is reloaded in wagons and transported to the Black Sea port of Burgas by railroad.

Tailings Management
At present, the final tailings gravitate over a distance of approximately 4 km to the tailings dam with 80-100% of the water reclaimed. The dam incorporates a seepage collection system at the dam wall toe which collects seepage water which is pumped back on to the impoundment. A system of monitors and piezometers maintains full controls potential phreatic water levels in the impoundment.
The dam wall will be fully reinforced to allow increased capacity.
To date the tailings dam contains approximately 10 million tonnes of tailings.
The company has available fresh water from three water sources, the principal one is owned by the Chelopech municipality, and the remaining water sources are owned by private enterprises.
The flotation plant and the underground mine are supplied with recycled water from the tailings dam, with mine waste water being transferred to the dam.